There are many optical and electro-optical applications where a microlens array or other array of one or more smoothly curved microstructures may be advantageously utilized. Microlenses for example find application in integrated optics applications such as for redirecting and focusing light waves confined along a waveguide. In microoptics, such lens arrays may be used for focusing, imaging or transmitting optical beams. Such arrays may also find application as phase shifting masks, laser beam homogenizers, or, where electrically conductive microstructures are employed, as the elements of flat panel displays.
However, the utility of such microstructures has heretofore been limited by limitations in techniques available for the fabrication thereof. For example, while the base diameter of each microlens or other microstructure may be 100 micrometers or more, there are applications where lenses or other structures of submicrometer size are desirable. Current techniques for fabricating microstructures are not capable of achieving dimensions much less than one micrometer. Current techniques, which frequently involve etching, also have trouble in avoiding interaction where structures are closely spaced and cannot be used with materials such as tin oxide or tungsten oxide which are difficult to etch and cannot otherwise be easily shaped. Tungsten oxide is a particularly desirable material in some applications since it is electrochromic conductive, changing color based on the current applied thereto. This is advantageous, for example, in producing flat screen displays.
Another limitation on existing techniques, using for example lithographic techniques for generating the microlens, is that the lens can only be formed on a flat substrate. However, there are applications, such as with contact lenses, where it may be desirable to form the microlens or other microstructures on a smoothly curved surface.
Still another limitation on microlenses formed using existing techniques is that it is not possible to achieve extremely smooth lens surfaces, resulting in microlenses of less than optimal quality. There are applications for microlenses where higher quality lens would be desirable. A further limitation with existing techniques is that they are generally limited to forming domed or hemispherical microstructures and are not easily adapted for forming structures having other shapes. Again, there are applications where microstructures having other shapes are desirable. Finally, existing techniques are relatively expensive and time consuming and often require skilled operators to achieve satisfactory results. A faster, less expensive technique for forming microstructures which is easier to practice and to automate is therefore desirable.